1. Field of the Invention
The present invention relates to a display apparatus including light emitting elements disposed in a display part.
2. Description of the Related Art
In recent years, much attention has been paid to an active matrix organic EL display apparatus including EL elements arranged in a matrix form on a substrate having TFTs (Thin Film Transistors).
For example, Japanese Patent Laid-Open No. 2003-316291 discloses one such apparatus, in which a second electrode is formed with a transparent electroconductive film across the whole surface on a light emission side of an image display part. When the transparent electroconductive film is formed to have a thickness of about 100 nm, it has a sheet resistance as high 100Ω/□ or greater, and thus power consumption occurs due to the high resistance of the transparent electroconductive film. To compensate for the power consumption, a first auxiliary wiring is disposed in the image display part. The first auxiliary wiring is connected to a second auxiliary wiring extending in a direction crossing the first auxiliary wiring. The second auxiliary wiring is connected via a contact hole to a wiring disposed in a periphery of a light emitting apparatus. The wiring extends around the light emitting apparatus and is connected to an input/output terminal (see FIGS. 2 to 4 in Japanese Patent Laid-Open No. 2003-316291).
In the technique disclosed in Japanese Patent Laid-Open No. 2003-316291, by providing the first auxiliary wiring, the second auxiliary wiring, and the wiring, a reduction is achieved in voltage difference across a second electrode plane. The wirings described above are formed using a material having lower resistance than that of the second electrode. This can cause a current to concentrate on the wirings. In the wirings disposed between the second electrode and the terminal (input/output terminal), the current concentration increases with position toward the terminal. More specifically, the current concentration increases in order of the first auxiliary wiring, the second auxiliary wiring, the wiring. In parts where the current concentration occurs, the wiring has relatively greater heat generation. Thus, greater heat generation occurs locally in a part close to the terminal than in the other parts in the light emitting apparatus. That is, heat generation increases in order of the first auxiliary wiring, the second auxiliary wiring, the wiring.
If there is a local part having high heat generation, influence of heat generation on light emitting elements disposed in the display part varies from one light emitting element to another, and thus nonuniformity occurs in characteristics of the light emitting elements across the display part. The influence of heat generation on light emitting elements is significantly great, in particular, when organic EL elements are used as the light emitting elements.